[WGSL] Generated switch statements are missing 'break' after each case

Inspect our metal output of https://webgpu.github.io/webgpu-samples/samples/bitonicSort#./bitonicCompute.frag.wgsl

The switch statement should have a break after each case, but it does not.

Generated metal:
....
    switch (global3.field2) {
    case 1:{
        vec<unsigned, 2> local8 = function1(parameter9.x, global3.field3);
        function0(local8.x, local8.y, global0, global4);
    }    case 2:{
        vec<unsigned, 2> local9 = function2(parameter9.x, global3.field3);
        function0(local9.x, local9.y, global0, global4);
    }    case 3:{
        vec<unsigned, 2> local10 = function1(parameter8.x, global3.field3);
        function3(local10.x, local10.y, global1, global2);
    }    case 4:{
        vec<unsigned, 2> local11 = function2(parameter8.x, global3.field3);
        function3(local11.x, local11.y, global1, global2);
    }    default:{
    }
...

each 'case' statement should have a break at the end of it